It is proposed to continue studies on the mechanism of genetic transcription as carried out by bacterial RNA polymerases, and on the action of regulatory factors which alter the specificity of transcription by those enzymes. These will include studies on the mechanism of RNA chain termination, the mechanism of transcriptional chain elongation and on the structure and specificity of sites that lead to pausing during in vitro elongation. The alteration of transcriptional specificity induced by binding to E. coli RNA polymerase of the regulatory nucleotide ppGpp will be studied. We will also study the role of a novel RNA polymerase in B. subtilis (RNA polymerase holoenzyme II), and determine the structure and function of its cognate promoter sites.